In the past, as an exhaust gas purification catalyst arranged in an exhaust passage of an internal combustion engine, there has been developed an electric heating catalyst (hereinafter referred to as an EHC) in which a catalyst is heated by means of a heater element which generates heat by electrical energization thereof.
In addition, in EHCs, there has been known a construction in which a pair of electrodes are connected to a side surface (an outer circumferential surface) of a heater element in a manner to oppose to each other (for example, see a first patent document). In such a construction, the heater element generates heat by an electric current that flows between the electrodes through the heater element.